1. Field of the Invention
The present invention relates to a hydrocarbon conversion process. More particularly, the invention relates to the alkylation of a paraffin with an olefin in the presence of an organic promoter that facilitates the formation of a high octane alkylate.
2. Description of the Prior Art
The use of catalytic alkylation processes to produce branched chain hydrocarbons having valuable anti-knock properties that are suitable for use as gasoline blending components is well known in the petroleum refining art. Generally, the alkylation of saturated hydrocarbons, such as isoparaffins, with olefins is accomplished by contacting the reactants with an acid catalyst, such as sulfuric acid, fluorosulfuric acid or a halogen acid such as hydrofluoric acid to form a reaction mixture, settling said mixture to separate the catalyst from the hydrocarbons, and further separating the hydrocarbons, for example by fractionation, to recover the alkylation reaction product. The alkylation reaction product is normally a mixture of C.sub.5 -C.sub.10 paraffins, often termed "alkylate", and typically contains a mixture of C.sub.8 -C.sub.9 hydrocarbons, the composition depending upon the particular paraffin and olefin utilized. The formation of more highly branched hydrocarbons, e.g. trimethylpentanes, rather than less branched hydrocarbons, e.g. dimethylhexanes, is preferred because the former provide a higher quality gasoline blending stock.
It is well known in the art that as the alkylation reaction proceeds, there will form a material that is effective in promoting the alkylation reaction. This material has been given a variety of names, including red oil, sludge, organic sludge, acid oil and the like (see, for example, U.S. Pat. Nos. 2,245,038; 2,375,637; 2,396,853; 2,413,759; 2,415,717; 2,418,146; 3,780,130). It has also been suggested that the octane number of the alkylate from sulfuric acid alkylation is a function of the composition of the acid (see Albright, L. F. et al, "Alkylation of Isobutane With Butenes: Effect of Sulfuric Acid Compositions", Ind. Eng. Chem. Process. Des. Develop., Vol. 11, No. 3, p. 446-450, 1972). However, none of the foregoing prior art teaches or suggests that the effectiveness of the organic promoter varies with temperature.